<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		.box{
			width:200px;
			height:50px;
			border:1px solid#999;
			text-align:center;
			line-height:50px;
			font-size:20px;
			margin:20px auto;
			background-color:#999;
		}
		.box:hover{
			background-color:#999;
		}

		.box ul{
			list-style-type:none;
			padding-left:0;
			margin:0 0 0 -1px;
			display:none;
		}
		.box ul li{
			width:200px;
			border:1px solid #999;
		}
		.box ul li:hover{
			background-color:#999;

		}
		.box:hover ul{
			display:block;
		}
	</style>
</head>
<body>
	<div class="box">
		菜单
		<ul>
			<li>01</li>
			<li>02</li>
			<li>03</li>
			<li>04</li>
		</ul>
	</div>
	
</body>
</html>